1. Technical Field
This disclosure relates generally to the field of electrical circuit breakers and more particularly to a multi-pole handle lock with same position handle control.
2. Description of the Related Art
In general, circuit breakers are employed to selectively engage a branch circuit to an electrical power supply. This function occurs by engaging and disengaging a pair of operating contacts for each phase of the circuit breaker. The circuit breaker provides protection against persistent overcurrent conditions and against the very high currents produced by short circuits. Typically, one of each pair of the operating contacts is supported by a pivoting contact arm while the other operating contact is substantially stationary. The contact arm is pivoted by an operating mechanism such that the movable contact supported by the contact arm can be engaged and disengaged from the stationary contact.
There are several ways by which the operating mechanism for the circuit breaker can disengage the operating contacts: the circuit breaker operating handle can be used to activate the operating mechanism; or a tripping mechanism, responsive to unacceptable levels of current carried by the circuit breaker, can be used to activate the operating mechanism; or auxiliary devices can be used to trip the circuit breaker thereby moving the movable contact. For many circuit breakers, the operating handle is coupled to the operating mechanism such that when the tripping mechanism activates the operating mechanism to separate the contacts, the operating handle moves to a fault or tripped position.
In multi-pole applications, like 220-240V branch circuits, two circuit breakers are combined together into a single unit. The combined unit is referred to as a single two pole breaker. Single multi-pole breakers incorporate “common trip”, which insures that when 1 pole trips, all of the other poles are tripped as well. Thus an overcurrent condition in any one pole will actuate a common tripping mechanism and shut off power to the entire multi-pole branch circuit. It is common practice within the industry to have an external handle tie attached across the handles of multi-pole breakers. Accordingly, the presence of the handle tie provides a visual indication that the handles are part of a combined unit having a common trip.
Handle locks are devices that can be installed on one or more circuit breakers to lock them in the on or off position, and prevent unauthorized switching. A problem arises when locking multiple handles all in the same position. Some devices that engage the handles so resembles an OEM traditional handle tie that it could give the erroneous illusion that the locked breakers are part of a single unit featuring a common trip. Accordingly, there is a need for a handle lock which allows same position locking of multiple breakers without visually blocking the free ends of the handles.